The subject of the present invention is the various polymorphic forms of benzyl (S,S)-2-(2-acetylsulphanylmethyl-3-benzo[1,3]dioxol-5-ylpropionylamino)propionate, called hereinafter Fasidotril, and the methods for preparing them. 
Fasidotril, benzyl (S,S)-2-(2-acetylsulphanylmethyl-3-benzo[1,3]dioxol-5-ylpropionylamino)propionate, may be prepared by applying the methods described in Patent EP 0,419,327 B1 or Patent FR 0014419 filed by Socixc3xa9txc3xa9 Civile Bioprojet and has advantageous properties as a mixed inhibitor of the enzymes enkephalinase (EC 3.4.24.11) and angiotensin converting enzyme (EC 3.4.15.1; ACE). It is indeed known that enkephalinase is a peptidase which degrades in particular enkephalins. Methionine and leucine enkephalin are peptides which were discovered in the brain and which are endogenous ligands for the morphine receptor. Moreover, the atrial natriuretic factor (ANF) is an endogenous peptide which exerts vasorelaxing, diuretic and natriuretic effects which are potentially beneficial in the treatment of cardiovascular and renal conditions. ANF is a substrate for enkephalinase and inhibitors of this peptidase slow its degradation, increase its plasma level and induce antihypertensive, diuretic and natriuretic effects (Lecomte et al., Proc. Natl. Ac. Sci. USA 1989, 86:19:7580-4).
It is also known, for example from French Patent No. 2,623,498 filed in the name of the applicant, that some amino acid derivatives exert an inhibitory activity on the enzyme for converting angiotensin I to angiotensin II (ACE), angiotensin II being an active vasomotor substance considered as the agent responsible for various forms of hypertension. These compounds are therefore useful for the treatment of hypertension and of cardiac insufficiency.
It has been discovered that Fasidotril can exist in various polymorphic crystalline forms which differ from each other in their physical and spectroscopic properties, their zones of thermodynamic stability and their methods of preparation. Four of these novel forms are described below and will be designated as form I, form II, form III and form IV, respectively.
It is shown that among these four forms, forms I and II are stable at low and high temperature, respectively, while forms III and IV are unstable and can be easily converted to the stable form I or II depending on the operating conditions chosen.
It is also shown that it is possible to convert form I to form II and to convert form II to form I depending on the operating conditions chosen.
The various polymorphic forms of Fasidotril may be prepared by crystallization, at a temperature of between the freezing point of the solution and the boiling point of the mixture, from a solution of Fasidotril in a solvent chosen from saturated hydrocarbons (for example pentane, cyclohexane) or unsaturated hydrocarbons (for example toluene, xylene), alcohols (for example methanol, ethanol, 2-propanol), ethers (for example diisopropyl ether, diethyl ether), esters (for example ethyl acetate, isopropyl acetate), amides (for example dimethylformamide, N-methyl-pyrrolidone, dimethylacetamide), nitriles (for example acetonitrile), halogenated solvents (for example dichloromethane, dichloroethane, chlorobenzene), water or a mixture of these solvents. This crystallization may be spontaneous or triggered by slow or rapid cooling, addition of a solvent, of seed crystals consisting of crystallized Fasidotril or another solid product, evaporation or distillation of the solvent. Furthermore, the initial Fasidotril solution may contain other products, for example an isomer of Fasidotril.
In the case, for example, of the preparation by spontaneous crystallization, it is possible to obtain form I by choosing a temperature of less than 25xc2x0 C., or form II by choosing a higher temperature, for example 50xc2x0 C., and maintaining this temperature for a sufficient period.
The various stable polymorphic forms of Fasidotril may also be prepared by conversion from one stable or metastable form to another. This conversion may be carried out in solution or in suspension by optionally seeding with a solid form of Fasidotril. This operation is carried out at a temperature between the freezing point of the solvent and its boiling point, in a solvent chosen from saturated hydrocarbons (for example pentane, cyclohexane) or unsaturated hydrocarbons (for example toluene, xylene), alcohols (for example methanol, ethanol, isopropanol), ethers (for example diisopropyl ether, diethyl ether), esters (for example ethyl acetate, isopropyl acetate), amides (for example dimethylformamide, N-methylpyrrolidone, dimethylacetamide), nitriles (for example acetonitrile), water or a mixture of these solvents.
The various polymorphic forms of Fasidotril may be characterized by X-ray diffraction (see FIG. 4), by differential scanning calorimetry, by infrared, by NMR of the solid or by any other method known to persons skilled in the art.
Form I has a novel X-ray powder diffraction spectrum (measurement carried out on a Siemens D5005 diffractometer with a copper anticathode; the results are exploited with the Eva v 7.0 software) with the following characteristic lines (2 theta in xc2x0):
17.1; 17.6; 17.9; 18.1; 18.8; 19.5; 20.0; 21.3; 22.1; 23.3; 24.8; 25.0; 27.8
The differential scanning calorimetry spectrum at 2xc2x0 C./min shows two maxima, one at 110.3xc2x0 C., the other at 114.1xc2x0 C. with enthalpies of 40.13 J/g and 65.47 J/g, respectively, and an onset of melting at 108.8xc2x0 C.
The infrared spectrum as a KBr tablet has the characteristic absorptions at the following wavelengths (in cmxe2x88x921, f for weak, m for average, F for strong):
3280 (F), 3080 (f), 3040 (f), 3000 (f), 2920 (m), 2800 (f), 1730 (F), 1690 (F), 1680 (F), 1640 (F), 1610 (f), 1540 (F), 1500 (F), 1480 (F), 1440 (F), 1400 (f), 1380 (m), 1360 (f), 1330 (m), 1310 (m), 1280 (m), 1260 (F), 1250 (F), 1220 (F), 1200 (F), 1130 (F), 1110 (F), 1060 (f), 1040 (F), 1010 (f), 1000 (f), 960 (F), 940 (f), 930 (m), 900 (m), 860 (f), 810 (m), 790 (m), 750 (F), 720 (f), 700 (F), 680 (f), 620 (F), 600 (f), 580 (f), 540 (f), 520 (f), 480 (f), 460 (f), 450 (f), 430 (f)
Form II has a novel X-ray powder diffraction spectrum (measurement carried out on a Siemens D5005 diffractometer with a copper anticathode; the results are exploited with the Eva v 7.0 software) with the following characteristic lines (2 theta in xc2x0):
8.1; 12.9; 16.2; 16.8; 17.3; 17.8; 18.4; 20.8; 23.8; 27.7
The differential scanning calorimetry spectrum at 2xc2x0 C./min shows a maximum at 114.8xc2x0 C. with an enthalpy of 101.64 J/g and an onset of melting at 112.6xc2x0 C.
The infrared spectrum as a KBr tablet has the characteristic absorptions at the following wavelengths (in cmxe2x88x921, f for weak, m for average, F for strong):
3320 (F), 3280 (F), 3080 (f), 3000 (f), 2920 (m), 2880 (m), 2800 (f), 1730 (F), 1690 (F), 1680 (F), 1640 (F), 1540 (F), 1500 (F), 1480 (F), 1440 (F), 1400 (f), 1380 (m), 1360 (m), 1330 (m), 1310 (m), 1280 (m), 1260 (F), 1220 (F), 1200 (F), 1160 (f), 1130 (F), 1110 (F), 1060 (f), 1040 (F), 1010 (f), 1000 (f), 960 (F), 940 (m), 930 (m), 900 (m), 860 (f), 810 (m), 790 (m), 750 (F), 700 (F), 620 (F), 600 (f), 580 (f), 540 (f), 520 (f), 480 (f), 460 (f), 430 (f).
Form III has a novel X-ray powder diffraction spectrum (measurement carried out on a Siemens D5005 diffractometer with a copper anticathode; the results are exploited with the Eva v 7.0 software) with the following characteristic lines (2 theta in xc2x0):
11.1; 12.2; 16.4; 16.7; 17.7; 17.9; 18.6; 19.1; 20.2; 20.6; 21.3; 22.2; 22.6; 24.2; 24.7; 26.8; 28.6
The differential scanning calorimetry spectrum at 0.2xc2x0 C./min shows four maxima at 101.3xc2x0 C., 103.6xc2x0 C., 105.9xc2x0 C. and 113.9xc2x0 C. with enthalpies of 3.62 J/g, 3.92 J/g, 1.61 J/g and 94.08 J/g, respectively, and onsets at 100.7xc2x0 C., 103.0xc2x0 C., 104.8xc2x0 C. and 112.1xc2x0 C., respectively.
Form IV has a novel X-ray powder diffraction spectrum (measurement carried out on a Siemens D5005 diffractometer with a copper anticathode; the results are exploited with the Eva v 7.0 software) with the following characteristic lines (2 theta in xc2x0):
8.8; 16.0; 17.2; 17.7; 18.4; 19.1; 19.3; 20.3; 21.3; 22.9; 25.1; 25.5; 26.5; 28.8
The differential scanning calorimetry spectrum at 0.2xc2x0 C./min shows three maxima at 90.4xc2x0 C., 103.0xc2x0 C. and 113.5xc2x0 C. with enthalpies of 1.32 J/g, 12.91 J/g and 96.10 J/g, respectively, with onsets at 87.0xc2x0 C., 101.5xc2x0 C. and 111.2xc2x0 C., respectively.
The present invention also relates to the pharmaceutical compositions containing, as active ingredient, Fasidotril in one of its polymorphic forms.
These compositions can be administered to humans by the oral, parenteral or rectal route.
These pharmaceutical compositions may be in solid or liquid form and may be provided in pharmaceutical dosage forms which are commonly used in human medicine such as, for example, in the form of plain or sugar-coated tablets, gelatin capsules, suppositories or preparations for injection.
The pharmaceutical compositions in accordance with the invention can be administered in unit doses, preferably of 1 to 200 mg of active ingredient and at a daily dosage which may range from 2 to 400 mg of active ingredient.
Advantageously, a pharmaceutical composition may comprise the stable form I or II, but it is also possible to prepare pharmaceutical compositions with forms III or IV.
The subject of the invention is also a method for treating a patient requiring treatment, by inhibiting enkephalinase and the angiotensin converting enzyme.
It relates in particular to a method of treating hypertension and/or cardiac insufficiency in which a pharmaceutical composition comprising one of the forms I, II, III or IV of Fasidotril is administered to a patient.
Preferably, and unless a delayed release form is used, this method envisages the administration of a daily dosage of between 2 and 400 mg of Fasidotril, preferably administered in the form of unit doses of 1 to 200 mg.
The subject of the invention is also the use of one of the forms I to IV to prepare a pharmaceutical composition as described above for the treatment of hypertension and/or cardiac insufficiency.
The examples given below illustrate the present invention without limiting it as a result.
In the following examples, Fasidotril is synthesized by any of the methods suited to Fasidotril and described in Patents EP 419 327 or FR 0014419. The purities of the polymorphic forms obtained after using the following examples are higher than 95% (precision limit of the analytical technique used).